There are various mechanisms in which a member must be actuated at regular intervals, but must be capable of being selectively disabled and enabled to eliminate the regular actuation of the member when desired. One such mechanism is a collator for printed signatures, in which a signature gripper at each of the collator supply boxes is normally actuated at regular intervals to feed signatures seriatim to the traveling signature gathering belt or saddle. The increasing popularity of demographic editions of periodicals, and the need to publish catalogs which contain many pages applicable to all parts of the country and other pages applicable only to certain regions, has made it necessary to develop collators in which certain signature grippers are selectively disabled and enabled in order that the collator may receive signatures fed by those grippers only when desired.
Collator grippers commonly are suction members which are oscillated to contact a signature at the bottom of a supply box while under vacuum and to swing away, pulling the signature which is then freed by release of the vacuum. Both the mechanical oscillation of the grippers and the regular actuation and release of the suction are accomplished by mechanisms which are a part of the collator drive, to eliminate timing problems. The vacuum control valve ordinarily is moved between an open position placing the grippers under vacuum and a closed position eliminating vacuum at the grippers by rotation of a cam shaft which is operated by the collator drive.
There has, for many years, been a need for a simple apparatus to selectively eliminate the regular connection of the grippers to suction, so that even though the grippers continue to oscillate they cannot feed signatures.
A mechanism which is capable of disabling and enabling the vacuum grippers of a collator is equally applicable to other mechanisms where a member which must be actuated at regular intervals needs to be selectively disabled and enabled.